a. Field of the Invention
The present invention relates to wheelchairs and, in particular, to a side frame assembly constructed of sub-upper and lower portions that are connected together without the use of welding.
b. Prior Art
Designing wheelchairs that are both adaptable and easy to manufacture has been particularly challenging. The typical wheelchair frame has a side frame with an upper member, a lower member, and one or more vertical members welded into place on the lower and/or upper side frame members. FIG. 1 illustrates a portion of a prior art welded frame 5 in which vertical support members 6 and 7 are welded into place. Although the vertical, welded members are typically necessary in order to provide vertical strength to the wheelchair frame, the welding process is time consuming and expensive. Furthermore, once a piece is welded into place on the side frame, it is impossible to move the location of the welded piece. Consequently, welded wheelchair side frames are both slow to manufacture and not versatile once the wheelchair has been constructed.
Welded frames have been used to manufacture small wheelchairs for children. The seat of the wheelchair is preferably low to the ground, so that a child can easily climb into the chair. To reduce the height of the chair, it is desirable to reduce the height of the sideframes. One approach to making relatively short sideframes has been to weld vertical support members between horizontal sideframe members, as FIG. 1 illustrates. These welded sideframes suffer from the same problems described above, namely, they are time consuming to manufacture and have a fixed, non-adaptable configuration.
An alternative type of sideframe is a one-piece, non-welded sideframe having an upper portion, a lower portion and at least one side portion. There are bends in the sideframe at the juncture of the upper portion with the side portion, and at the juncture of the side portion and the lower portion. The bend is typically a portion of a circle. Sideframes having a height as measured from the bottom of the lower portion to the top of the upper portion of approximately nine (9) inches have been achieved with this design. However, it is very difficult, if not impossible, to manufacture a one-piece, non-welded design of this sort that is short enough for a small child""s wheelchair, in which the sideframe can be as short as six (6) inches or less. The radius of curvature of the bends that join the upper, side and lower portions would need to be prohibitively tight for standard tubular sideframe members.
There is, therefore, a need in the art for a wheelchair side frame design that is easier to construct and more versatile than known wheelchair designs utilizing welds. Furthermore, there is a need for a non-welded sideframe construction that can be used to construct small sideframes for use in children""s"" wheelchairs.
In light of the problems inherent with welded sideframes, the present invention presents an improved and more adaptable sideframe design than is known in the art. The present invention includes a wheelchair side frame having an upper member and a lower member separate from the upper member. The upper member is removably interconnected with the lower member, and the sideframe is generally free of welds. This two-piece, nonwelded configuration is especially useful in designing short wheelchairs for children, although it also can be used for larger wheelchairs.
In accordance with one particular embodiment of the present invention, a sideframe for a wheelchair has a top frame and a separate bottom frame. An axle plate extends between and is attached to the top and bottom frames, thereby interconnecting the top and bottom frames. A caster plate is attached to the sideframe, and the top frame and the bottom frame are removably attached to one another.
The sideframe may have a variety of additional features. The top and bottom frames may each comprise a plurality of bolt apertures. Similarly, the axle plate and the axle extension plate each comprise a plurality of bolt apertures. In an arrangement for support a rear-mounted major wheel, the axle plate is to the rear of the sideframe and the caster plate is to the front of the sideframe. In an alternative arrangement for supporting a front-mounted major wheel, an axle plate is to the front of the sideframe and the caster plate is to the rear of the sideframe.
In accordance with further alternative features, the top frame may comprise an upper portion and a downwardly extending rear portion. The downwardly-extending rear portion may be removably attached to the lower frame member. The downwardly extending portion may include a concave end piece adapted for engagement with the lower frame member, which may have a variety of different cross-sections, including tubular. In either arrangement, the caster plate may be attached to the bottom member and to the top member to interconnect the bottom member with the upper member
In accordance with another aspect of the present invention, a wheelchair frame comprises left and right sideframes. The sideframes are removably connected to one another by at least one connecting member extending in between and connected to the first and second sideframes, respectively. The connecting member may include one or more concave end pieces adapted to interconnect with the top and bottom members. The concave end pieces may each have a bolt receptor. The frame may include an anti-tip member extending rearwardly or forwardly therefrom. The anti-tip member may include one or more wheels such that the anti-tip member rolls along the ground with the major wheel.
The proceeding generally summarizes major points of the invention. However, additional points and objects of the invention may be gleaned from the Detailed Description of the preferred embodiments, from the drawings, and from the claims. Consequently, this Summary is not to be viewed as limiting the scope of the invention.